Visual signal devices are widely used in industrial applications, such as warehouses, loading docks, manufacturing facilities, or other settings where a machine status indicator, safety indicator, or alarm indicator is provided in the form of color-coded signals. For example, signal tower lights, also referred to as stack lights, can be placed on a forklift, tugger, pallet jack, order picker or other manned vehicle or equipment to provide a status indication in the form of a color-coded signal. Such color coded signals can be useful to those operating or in proximity to such equipment for providing safety and status indications. In addition to manned mobile equipment, such signal towers can also be used on stationary equipment, for the same status and safety purposes.
Typical signal tower lights include a group of color emitting modules stacked one on top of the other. Each module emits a single color. Each module comprises a colored lens, permitting a corresponding color to be emitted when the module is activated (or turned “on”). The combination of colors in a signal tower light are chosen based on a user's needs, and the signals to be communicated, wherein the colors of the modules are chosen to indicate the existence of possible predefined conditions.
For example, as illustrated in FIG. 1, a five-level signal tower light 100 comprises five modules 110-150, each module having a colored lens for emitting a single color based on the color of the lens. As an example, module 110 can include a red lens, module 120 can include a yellow lens, module 130 can include a green lens, etc. In this manner, each color or combination of individual colors can be associated with a predefined condition. For example, the red module 110, when turned on, can indicate a warning or alarm as a first predefined condition, i.e., “stop.” The yellow module 120, when turned on, can indicate “caution” as a second predefined condition, as another example. The colors are typically chosen as a function of the equipment or environment, or both. The conventional signal tower light, therefore, is a relatively tall and narrow stack of colored lights, such as the signal tower 100 illustrated in FIG. 1. The more modules that are added to the stack, the taller the signal tower light.
Signal towers, such as that of FIG. 1, can be mounted to stationary or mobile equipment. To do so, signal tower 100 is often mounted on a pole 160 and a base 170 arrangement to improve visibility. In such instances, the increased height of the signal tower light is an acceptable trade-off relative to any increased vulnerability to the light, or other property, created by such additional height. That is, even if not ideal, in order to achieve the correct number of lights for the relevant conditions being monitored or for desired visibility, a certain amount of height could be unavoidable. In particular, when mounted to mobile equipment, there is the challenge of mounting the lights high enough that they are clearly visible and low enough that they can fit through doorways. Also, while FIG. 1 shows a five level stack light, on mobile equipment it is also common to mount a single light on a pole. Nevertheless, even when there is only a single light, the height issues remain.